Name: electrophysiological recording from drosophila trichoid sensilla in response to odorants of low volatility
Uploaded: 2017-07-27T15:00:00
Description: Watch this Scientific Journal Video about Electrophysiological Recording from Drosophila Trichoid Sensilla in Response to Odorants of Low Volatility at JoVE.com

We thank Ye Zhang for the help with the sample traces and Tin Ki Tsang for the help with the pictures. This work was supported by a Ray Thomas Edwards Foundation Early Career Award and an NIH grant (R01DC015519) to C.-Y.S. and NIH grants (R01DC009597 and R01DK092640) to J.W.W.

1. Preparation of the Hardware for at4 Recording
<ol>
	<li>Use a pipette puller instrument to prepare electrodes with aluminosilicate glass capillaries (O.D 1.0 mm, I.D. 0.64 mm). Blunt the tip of the reference electrode slightly with a pair of fine forceps to facilitate insertion into the clypeus of the fly (i.e.&#160;a rounded plate at the front of the fly head, above the mouthparts). 
	NOTE: 7-day-old WT males (Berlin) were used in this study. Use AHL saline solution14 as the el...

<ol>
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I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Olfactory+processing+and+behavior+downstream+from+highly+selective+receptor+neurons.">Olfactory processing and behavior downstream from highly selective receptor neurons.</a> Nat Neurosci. 10 (5), 623-630 (2007).</li><li>Laughlin, J. D., Ha, T. S., Jones, D. N. M., Smith, D. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Activation+of+Pheromone-sensitive+neurons+is+mediated+by+conformational+activation+of+pheromone-binding+protein.">Activation of Pheromone-sensitive neurons is mediated by conformational activation of pheromone-binding protein.</a> Cell. 133 (7), 1255-1265 (2008).</li><li>Gomez-Diaz, C., Reina, J. H., Cambillau, C., Benton, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ligands+for+pheromone-sensing+neurons+are+not+conformationally+activated+odorant+binding+proteins.">Ligands for pheromone-sensing neurons are not conformationally activated odorant binding proteins.</a> PLoS Biol. 11 (4), e1001546 (2013).</li><li>Dweck, H. K. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pheromones+mediating+copulation+and+attraction+in+Drosophila.">Pheromones mediating copulation and attraction in Drosophila.</a> Proc Nat Acad USA. 112, 2829-2835 (2015).</li><li>Cappa, C. D., Lovejoy, E. R., Ravishankara, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaporation+rates+and+vapor+pressures+of+the+even-numbered+C8-C18monocarboxylic+acids.">Evaporation rates and vapor pressures of the even-numbered C8-C18monocarboxylic acids.</a> J Phys Chem A. 112 (17), 3959-3964 (2008).</li><li>Kimura, K. -. I., Sato, C., Yamamoto, K., Yamamoto, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=From+the+back+or+front:+the+courtship+position+is+a+matter+of+smell+and+sight+in+Drosophila+melanogaster+males.">From the back or front: the courtship position is a matter of smell and sight in Drosophila melanogaster males.</a> J Neurogenet. 29 (1), 18-22 (2015).</li><li>Grosjean, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+olfactory+receptor+for+food-derived+odours+promotes+male+courtship+in+Drosophila.">An olfactory receptor for food-derived odours promotes male courtship in Drosophila.</a> Nature. 478 (7368), 236-240 (2011).</li><li>Wang, J. W., Wong, A. M., Flores, J., Vosshall, L. B., Axel, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-photon+calcium+imaging+reveals+an+odor-evoked+map+of+activity+in+the+fly+brain.">Two-photon calcium imaging reveals an odor-evoked map of activity in the fly brain.</a> Cell. 112 (2), 271-282 (2003).</li><li>Pellegrino, M., Nakagawa, T., Vosshall, L. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single+sensillum+recordings+in+the+insects+Drosophila+melanogaster+and+Anopheles+gambiae.">Single sensillum recordings in the insects Drosophila melanogaster and Anopheles gambiae.</a> J Vis Exp. (36), e1-e5 (2010).</li></ol>

Here, we described a procedure by which the responses of Or47b ORNs to palmitoleic acid can be robustly induced and recorded. We modified a conventional long-distance odor delivery method2,7,10 to troubleshoot the problem of insufficient pheromone odorant delivery. We addressed the issue of low odorant volatility by delivering the compound via odorant cartridges, the opening of which are positioned within millimeters of the prep...

Drosophila ORNs respond to a vast number of odorants, with widely ranging carbon chain lengths and a variety of functional groups, including esters, alcohols, ketones, lactones, aldehydes, terpenes, organic acids, amines, sulfur compounds, heterocyclics, and aromatics2,3. Odorants varied in their physicochemical features can have markedly different volatilities, indicated by the vapor pressure of the compound. Notably, biologically relevant odorants for Drosophila melanogaster differ tremendously in their volatility. For example, Ir92a ORNs respond to ammonia4, which is highly volatile, with a vapor pressure of 6,432 mmHg at 20 &#176;C. In contrast, Or67d ORNs respond to a male pheromone, cis-vaccenyl acetate (cVA)5,6, the vapor pressure of which is 43 mmHg at 20 &#176;C.
Studying the olfactory response to odorants of low volatility is particularly challenging with conventional odor-delivery methods, in which odorants are delivered via a carrier air stream over a relatively long distance (i.e.&#160;several centimeters). As such, the reported olfactory responses to a given low-volatility odorant can vary greatly, depending on the design of the odor-delivery system. For example, the reported response of Or67d ORNs to a high dose of cVA ranges from ~407&#160;- &#62;200 spikes/s6. Moreover, the ineffective delivery of cVA with conventional delivery methods is likely attributed to false-negative results, leading to the interpretation that cVA by itself is not sufficient to activate Or67d ORNs8. This interpretation was later challenged by another study using a close-range odor-delivery method9. It is therefore imperative to develop a robust odor-delivery system for the effective presentation of odorants of low volatility.
Recently, we identified several long-chain cuticular fatty acids as ligands for Or47b ORNs. They are housed in the type 4 Antennal Trichoid Sensillum (at4). Among the long-chain fatty acid odorants, we found that palmitoleic acid functions as an aphrodisiac pheromone that promotes male courtship by activating Or47b ORNs1. However, in another study using a conventional odor-delivery method, methyl laurate was shown to elicit responses from Or47b ORNs, while palmitoleic acid evoked no response when presented from the same distance10. Compared to cVA, long-chain fatty acids are even less volatile, with vapor pressures less than 0.001 mmHg at 25 &#176;C11. The inherently low volatility of long-chain fatty acid odorants, which precludes efficient presentation to the antenna via conventional odor-delivery systems, likely accounted for the false-negative results10. This inconsistency highlights the inadequacy of conventional odor-delivery systems in presenting low-volatility odorants. It was previously shown that the effective delivery of fly cuticular odors requires close proximity between the odor source and the target tissue6. Thus, to fully characterize the effects of biologically active pheromones while mimicking the distance from which they are likely encountered by fruit flies in nature12,13, we agreed that minimal distance must be accorded high priority in our procedure.
Our method holds further advantages, including compatibility with standard electrophysiology rigs and techniques. Pre-existing rig setups require minimal modification to accommodate this protocol, and most SSR steps require only minor adjustments. This renders our technique readily accessible to researchers experienced in SSR. Furthermore, our technique allows for the presentation of low-volatility odorants with sharp onset and offset, correlating stimulus delivery with neuronal response. Finally, the hardware layout facilitates rapid exchanges between odorant cartridges, expediting data collection over a desired dosage range.
We begin by reviewing the preparation of reference and recording electrodes, Adult Hemolymph-Like (AHL) solution, odorant delivery cartridges, and the corresponding olfactometer. We then discuss the preparation of the palmitoleic acid odorant solutions, followed by the preparation of the fly for recording. We proceed to consider the criteria for selecting a trichoid sensillum to record and more closely examine the positioning of the odorant cartridge before presenting representative data acquired using this method. Finally, we conclude by exploring useful applications of this technique, some encountered issues, and their solutions.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Prep Setup &#38; Miscellaneous Materials</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Pipette Puller Instrument&#160;</td>
			<td>Sutter Instruments 
			Novato CA USA</td>
			<td>P97</td>
			<td>Pipette Puller</td>
		</tr>
		<tr>
			<td>Borosilicate Glass Capillaries</td>
			<td>World Precision Instruments 
			Sarasota FL USA</td>
			<td>1B100F-4</td>
			<td>to make holding rods</td>
		</tr>
		<tr>
			<td>Aluminosilicate Glass Capillaries&#160;</td>
			<td>Sutter Instruments 
			Novato CA USA</td>
			<td>AF100-64-10</td>
			<td>to make electrodes</td>
		</tr>
		<tr>
			<td>Superfrost Microscope Slides</td>
			<td>Fisher Scientific 
			Pittsburgh PA USA</td>
			<td>12-550-143</td>
			<td>for fly-prep station</td>
		</tr>
		<tr>
			<td>Permanent Double Sided Tape</td>
			<td>Scotch 
			St. Paul MN USA</td>
			<td>NA</td>
			<td>for fly-prep station</td>
		</tr>
		<tr>
			<td>Upright microscope</td>
			<td>Olympus 
			Shinjuku Tokyo Japan</td>
			<td>BX51</td>
			<td>for recording rig</td>
		</tr>
		<tr>
			<td>Plastalina modeling clay</td>
			<td>Van Aken 
			North Charleston SC USA</td>
			<td>B0019QZMQQ</td>
			<td>for prep station and to stablize the holding rod</td>
		</tr>
		<tr>
			<td>Rapid-Flow Sterile Disposable Filter Unit with SFCA Membrane, 0.45 mm</td>
			<td>Nalgene 
			Rochester NY USA</td>
			<td>#156-4045</td>
			<td>to sterilize AHL solution</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company&#160;&#160;&#160;</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Cartridge Materials</td>
			<td>&#160;&#160;&#160;</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>200 &#181;L pipette tip&#160;</td>
			<td>VWR 
			Radnor PA USA</td>
			<td>53508-810</td>
			<td>to make odor cartridges and fly prep</td>
		</tr>
		<tr>
			<td>Filter Paper</td>
			<td>Whatman 
			Maidstone Kent UK</td>
			<td>740-E</td>
			<td>to make odor cartridges&#160;</td>
		</tr>
		<tr>
			<td>Vacuum Desiccator&#160;</td>
			<td>Cole-Parmer 
			Vernon Hills IL USA</td>
			<td>VX-06514-30</td>
			<td>to vaporize ethanol solvent</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company&#160;&#160;&#160;</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Odorant Materials</td>
			<td>&#160;&#160;&#160;</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>cis-palmitoleic acid</td>
			<td>Cayman Chemical 
			Ann Arbor MI USA</td>
			<td>#10009871 (CAS # 373-49-9)</td>
			<td>Or47b odorant</td>
		</tr>
		<tr>
			<td>trans-palmitoleic acid</td>
			<td>Cayman Chemical 
			Ann Arbor MI USA</td>
			<td>#9001798 (CAS # 10030-73-6)</td>
			<td>Or47b odorant</td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Spectrum Chemical MFG.&#160; 
			New Brunswick NJ USA</td>
			<td>E1028-500MLGL</td>
			<td>to dilute palmitoleic acid&#160;</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company&#160;&#160;&#160;</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Rig Setup Materials</td>
			<td>&#160;&#160;&#160;</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Odorant Cartridge Micromanipulator</td>
			<td>Siskiyou 
			Grants Pass OR USA</td>
			<td>MX130R</td>
			<td>to position the olfactometer</td>
		</tr>
		<tr>
			<td>Flow Vision software&#160;</td>
			<td>Alicat 
			Tuscon AZ USA</td>
			<td>FLOWVISIONSC</td>
			<td>software to control flow rate</td>
		</tr>
		<tr>
			<td>Mass Controller</td>
			<td>Alicat 
			Tuscon AZ USA</td>
			<td>MC-2SLPM-D</td>
			<td>to control the flow rate for humidified air</td>
		</tr>
		<tr>
			<td>Mass Controller</td>
			<td>Alicat 
			Tuscon AZ USA</td>
			<td>MC-500SCCM-D</td>
			<td>to control the flow rate for odor stimulation</td>
		</tr>
		<tr>
			<td>Clampex</td>
			<td>Molecular Devices 
			Sunnyvale CA USA</td>
			<td>Ver. 10.4</td>
			<td>Data acquisition software</td>
		</tr>
		<tr>
			<td>Air delivery tube</td>
			<td>Ace Glass 
			Vineland NJ USA</td>
			<td>8802-936&#160;</td>
			<td>to deliver humidified air</td>
		</tr>
		<tr>
			<td>50x objective lens&#160;</td>
			<td>Olympus 
			Shinjuku Tokyo Japan</td>
			<td>LMPLFL50X</td>
			<td>recording rig</td>
		</tr>
		<tr>
			<td>Clampfit 10</td>
			<td>Molecular Devices 
			Sunnyvale CA USA</td>
			<td>Ver. 10.4</td>
			<td>software for spike analysis&#160;</td>
		</tr>
		<tr>
			<td>Igor Pro 6</td>
			<td>WaveMetrics 
			Lake Oswego OR USA</td>
			<td>Ver. 6.37</td>
			<td>software for data analysis&#160;</td>
		</tr>
		<tr>
			<td>Audio Monitor</td>
			<td>ALA Scientific Instruments 
			Farmingdale NY USA</td>
			<td>NPIEXB-AUDIS-08B</td>
			<td>Aurally reports individual spikes</td>
		</tr>
		<tr>
			<td>Extracellular Amplifier</td>
			<td>ALA Scientific Instruments 
			Farmingdale NY USA</td>
			<td>NPIEXT-02F</td>
			<td>to increase the amplitude of electrical signals</td>
		</tr>
		<tr>
			<td>Valve Controller</td>
			<td>Warner Instruments&#160;&#160;&#160;</td>
			<td>VC-8</td>
			<td>to control the opening of the valve for odor stimulation</td>
		</tr>
		<tr>
			<td>Recording Electrode Micromanipulator</td>
			<td>Sutter Instruments 
			Novato CA USA</td>
			<td>MP-285</td>
			<td>to position recording electrode</td>
		</tr>
		<tr>
			<td>Headstage Amplifier</td>
			<td>ALA Scientific Instruments 
			Farmingdale NY USA</td>
			<td>EQ-16.0008</td>
			<td>to increase the amplitude of electrical signals</td>
		</tr>
		<tr>
			<td>Oscilloscope</td>
			<td>Tektronix 
			Beaverton OR USA</td>
			<td>TDS2000C</td>
			<td>Visual report of individual spikes</td>
		</tr>
	</tbody>
</table>

electrophysiological recording from drosophila trichoid sensilla in response to odorants of low volatility

Insects rely on their sense of smell to guide a wide range of behaviors that are critical for their survival, such as food-seeking, predator avoidance, oviposition, and mating. Myriad chemicals of varying volatilities have been identified as natural odorants that activate insect Olfactory Receptor Neurons (ORNs). However, studying the olfactory responses to low-volatility odorants has been hampered by an inability to effectively present such stimuli using conventional odor-delivery methods. Here, we describe a procedure that permits the effective presentation of low-volatility odorants for in vivo Single-Sensillum Recording (SSR). By minimizing the distance between the odor source and the target tissue, this method allows for the application of biologically salient but hitherto inaccessible odorants, including palmitoleic acid, a stimulatory pheromone with a demonstrated effect on ORNs involved in courtship and mating behavior1. Our procedure thus affords a new avenue to assay a host of low-volatility odorants for the study of insect olfaction and pheromone communication.

Our technique was successfully applied to determine the relative efficacy of the trans (Figure 5A) versus cis (Figure 5B) isomers of palmitoleic acid. Our representative data demonstrates that trans-palmitoleic acid is a more effective ligand for Or47b ORNs when compared to the cis isoform (Figure 5C). A single neuron was recorded from each fly, with twelve flies r...

Watch this Scientific Journal Video about Electrophysiological Recording from Drosophila Trichoid Sensilla in Response to Odorants of Low Volatility at JoVE.com

Electrophysiological Recording from Drosophila Trichoid Sensilla in Response to Odorants of Low Volatility

The overall goal of this protocol is to demonstrate how to present odorants of low volatility for single-sensillum recording from Drosophila olfactory receptor neurons that respond to long-chain cuticular pheromones.

Electrophysiological Recording from Drosophila Trichoid Sensilla in Response to Odorants of Low Volatility

Insects rely on their sense of smell to guide a wide range of behaviors that are critical for their survival, such as food-seeking, predator avoidance, ...

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